If you can't see the Plots: Style options, click on the little right arrow to the left of "Plots: Style" to make it point down; that will open the Plots: Style panel.

Options available here include:

Plot Background Color Choose between "black" and "white" as the background color for your plots

Percent per Contour Enter the percent of cells represented by each contour

Outliers Start At Set the percent at which outliers are displayed

Smoothing The level of smoothing for a plot type.

Aspect Ratio Specify the height/width ratio for histograms